Community Web Portals (e.g., digital libraries, vertical aggregators, infomediaries) have become quite popular nowadays in supporting specific communities of interest on corporate intranets or the Web. Portal Catalogs, organize and describe various information resources (e.g., sites, documents, data) for diverse target audiences (corporate, interenterprise, e-marketplace, etc.), in a multitude of ways, which are far more flexible than those provided by standard databases. In this paper, we propose a declarative language suitable for querying Portal Catalogs created according to the Resource Description Framework (RDF) W3C standard. Our language, called RQL, relies on a formal graph model, that captures the RDF modeling primitives and permits the interpretation of superimposed descriptions by means of one or more schemas. In this context, RQL adapts the functionality of semistructured query languages to the peculiarities of RDF but also extends this functionality in order to uniformly query both resource descriptions and related schemas. RQL is used in several projects aiming at building, accessing and personalizing Community Web Portals.